The safety of milk powder is closely related to everyone’s life. In the production of milk powder, it is often easy to mix in foreign bodies, such as light and thin plastic, insects, metals, and other foreign bodies. In this paper, THz spectroscopy is used to detect common foreign bodies in milk powder, such as polymer materials (i.e., PP, PVC, and PE), insects, and metal gaskets. The detection of foreign bodies in milk powder can be realized by using THz spectroscopy combined with random forest discrimination method, and the recognition accuracy rate reaches 100%. The accuracy rate also reaches 100% when the types of foreign bodies are distinguished, thus, successfully realizing the identification and qualitative discrimination of foreign bodies in milk powder. At the same time, THz imaging technology is used to detect milk powder with foreign bodies. The outline and the boundaries of foreign bodies in milk powder are clear in the imaging from 0.5 to 1.0 THz. Thus, the size and shape of foreign bodies in milk powder can be well distinguished. This experiment verifies the feasibility of qualitative detection of foreign bodies in milk powder by the combination of terahertz imaging and spectrum, and established a better random forest detection model, which proposes a solution to ensure the safety of milk powder.

奶粉的安全与每个人的生活息息相关。在奶粉生产中，往往容易混入异物，如轻薄的塑料、昆虫、金属等异物。本文采用太赫兹光谱检测奶粉中常见的异物，如高分子材料（即PP、PVC、PE）、昆虫、金属垫片等。采用太赫兹光谱结合随机森林判别法可实现奶粉中异物的检测，识别准确率达到100%。异物种类鉴别准确率也达到100%，从而成功实现了奶粉中异物的鉴别定性鉴别。同时，太赫兹成像技术用于检测含异物的奶粉。0.5~1.0THz成像，奶粉中异物轮廓清晰，边界清晰。因此，可以很好地区分奶粉中异物的大小和形状。本实验验证了太赫兹成像与光谱相结合对奶粉中异物进行定性检测的可行性，建立了较好的随机森林检测模型，提出了保障奶粉安全的解决方案。